/omemo commands for transport and chats

e2ee/omemo/encrypt.go

@@ -59,6 +59,16 @@ func (b *Backend) Encrypt(from e2ee.PeerID, to []e2ee.PeerID, plaintext []byte)
 		}
 
 		for _, deviceID := range deviceIDs {
+			// A manually blocked device (see Backend.BlockDevice) never
+			// gets a copy, regardless of any session already established
+			// with it - TOFU trust itself is untouched, this is purely the
+			// manual override layered on top.
+			if blocked, err := store.IsDeviceBlocked(string(peer), deviceID); err != nil {
+				return e2ee.Envelope{}, fmt.Errorf("omemo: IsDeviceBlocked(%s:%d): %w", peer, deviceID, err)
+			} else if blocked {
+				continue
+			}
+
 			cipher, err := libsignal.NewSessionCipher(b.libctx, storeCtx, libsignal.Address{Name: string(peer), DeviceID: deviceID}, version.libsignalVersion())
 			if err != nil {
 				return e2ee.Envelope{}, fmt.Errorf("omemo: NewSessionCipher(%s:%d): %w", peer, deviceID, err)
@@ -116,6 +126,17 @@ func (b *Backend) Decrypt(from, to e2ee.PeerID, env e2ee.Envelope) ([]byte, erro
 	if err := b.ensureIdentity(store); err != nil {
 		return nil, fmt.Errorf("omemo: ensureIdentity: %w", err)
 	}
+
+	// A manually blocked sender device (see Backend.BlockDevice) is
+	// rejected outright, regardless of any session already established
+	// with it - TOFU trust itself is untouched, this is purely the manual
+	// override layered on top.
+	if blocked, err := store.IsDeviceBlocked(string(from), wireEnv.SenderSID); err != nil {
+		return nil, fmt.Errorf("omemo: IsDeviceBlocked: %w", err)
+	} else if blocked {
+		return nil, fmt.Errorf("omemo: Decrypt: sender device %s:%d is blocked", from, wireEnv.SenderSID)
+	}
+
 	regID, err := store.GetLocalRegistrationID()
 	if err != nil {
 		return nil, fmt.Errorf("omemo: GetLocalRegistrationID: %w", err)

e2ee/omemo/identity.go

@@ -486,14 +486,91 @@ func (b *Backend) Devices(owner, peer e2ee.PeerID) ([]e2ee.DeviceInfo, error) {
 	infos := make([]e2ee.DeviceInfo, 0, len(deviceIDs))
 	for _, id := range deviceIDs {
 		// A stored session implies IsTrustedIdentity already accepted this
-		// device's key (TOFU) - finer-grained trust states (manually
-		// verified/revoked) are a documented future enhancement, not
-		// needed for this phase.
-		infos = append(infos, e2ee.DeviceInfo{ID: e2ee.DeviceID(strconv.FormatUint(uint64(id), 10)), Trusted: true})
+		// device's key (TOFU, which always stays on) - Trusted here
+		// reflects the separate manual block override layered on top (see
+		// BlockDevice), not TOFU's own verdict.
+		blocked, err := store.IsDeviceBlocked(string(peer), id)
+		if err != nil {
+			return nil, fmt.Errorf("omemo: IsDeviceBlocked(%s:%d): %w", peer, id, err)
+		}
+		infos = append(infos, e2ee.DeviceInfo{ID: e2ee.DeviceID(strconv.FormatUint(uint64(id), 10)), Trusted: !blocked})
 	}
 	return infos, nil
 }
 
+// Override implements e2ee.Backend.
+func (b *Backend) Override(owner e2ee.PeerID) (bool, bool, error) {
+	login, ownerJID, ok := e2ee.SplitOwnedPeer(owner)
+	if !ok {
+		return false, false, fmt.Errorf("omemo: Override: %q is not an OwnedPeer", owner)
+	}
+
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	return b.db.Store(b.libctx, login, ownerJID).Override()
+}
+
+// SetOverride implements e2ee.Backend.
+func (b *Backend) SetOverride(owner e2ee.PeerID, on bool) error {
+	login, ownerJID, ok := e2ee.SplitOwnedPeer(owner)
+	if !ok {
+		return fmt.Errorf("omemo: SetOverride: %q is not an OwnedPeer", owner)
+	}
+
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	return b.db.Store(b.libctx, login, ownerJID).SetOverride(on)
+}
+
+// ClearOverride implements e2ee.Backend.
+func (b *Backend) ClearOverride(owner e2ee.PeerID) error {
+	login, ownerJID, ok := e2ee.SplitOwnedPeer(owner)
+	if !ok {
+		return fmt.Errorf("omemo: ClearOverride: %q is not an OwnedPeer", owner)
+	}
+
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	return b.db.Store(b.libctx, login, ownerJID).ClearOverride()
+}
+
+// BlockDevice implements e2ee.Backend.
+func (b *Backend) BlockDevice(owner, peer e2ee.PeerID, device e2ee.DeviceID) error {
+	login, ownerJID, ok := e2ee.SplitOwnedPeer(owner)
+	if !ok {
+		return fmt.Errorf("omemo: BlockDevice: %q is not an OwnedPeer", owner)
+	}
+	deviceID, err := parseDeviceID(device)
+	if err != nil {
+		return err
+	}
+
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	return b.db.Store(b.libctx, login, ownerJID).SetDeviceBlocked(string(peer), deviceID, true)
+}
+
+// UnblockDevice implements e2ee.Backend.
+func (b *Backend) UnblockDevice(owner, peer e2ee.PeerID, device e2ee.DeviceID) error {
+	login, ownerJID, ok := e2ee.SplitOwnedPeer(owner)
+	if !ok {
+		return fmt.Errorf("omemo: UnblockDevice: %q is not an OwnedPeer", owner)
+	}
+	deviceID, err := parseDeviceID(device)
+	if err != nil {
+		return err
+	}
+
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	return b.db.Store(b.libctx, login, ownerJID).SetDeviceBlocked(string(peer), deviceID, false)
+}
+
 func (b *Backend) Enabled(owner e2ee.PeerID) (bool, error) {
 	login, ownerJID, ok := e2ee.SplitOwnedPeer(owner)
 	if !ok {

e2ee/policy.go

@@ -0,0 +1,83 @@
+package e2ee
+
+import "fmt"
+
+// Mode is the account-wide OMEMO policy (see persistence.Session.OMEMO),
+// combined with a chat's optional Override and its auto-upgrade sticky
+// flag (Backend.Enabled) by ShouldEncrypt to decide whether to attempt
+// outgoing encryption for that chat right now.
+type Mode int
+
+const (
+	// ModeAuto (the default) only encrypts once a chat has auto-upgraded
+	// (Backend.Enabled), i.e. its peer has already sent this chat an OMEMO
+	// message. This is the original, only behavior before Mode existed.
+	ModeAuto Mode = iota
+
+	// ModeOn always attempts to encrypt, regardless of whether the peer
+	// has ever shown OMEMO support. If no session can be established, the
+	// send fails outright rather than falling back to plaintext - the
+	// same OMEMOSendFailedBody convention already used at every Encrypt
+	// call site applies, it's just reached unconditionally now instead of
+	// only for already-active chats. Incoming plaintext is still accepted
+	// and processed as usual - this mode only ever affects outgoing.
+	ModeOn
+
+	// ModeOff never encrypts outgoing content, even for a chat that has
+	// already auto-upgraded - inbound OMEMO messages are still decrypted
+	// normally regardless of this mode (decryption never consults Mode at
+	// all, only the encrypt hooks do).
+	ModeOff
+)
+
+func (m Mode) String() string {
+	switch m {
+	case ModeOn:
+		return "on"
+	case ModeOff:
+		return "off"
+	default:
+		return "auto"
+	}
+}
+
+// ParseMode maps persistence.Session.OMEMO's stored string to a Mode - an
+// empty string (an account that predates this field, or never touched it)
+// is treated the same as "auto", matching Mode's zero value and default.
+func ParseMode(s string) (Mode, error) {
+	switch s {
+	case "", "auto":
+		return ModeAuto, nil
+	case "on":
+		return ModeOn, nil
+	case "off":
+		return ModeOff, nil
+	default:
+		return ModeAuto, fmt.Errorf("e2ee: unknown mode %q (want on, auto, or off)", s)
+	}
+}
+
+// ShouldEncrypt decides whether owner's outgoing content should be
+// encrypted right now, combining (in priority order): owner's explicit
+// per-chat Override, if one has been set; otherwise mode's account-wide
+// policy, consulting backend's auto-upgrade sticky flag (Enabled) only for
+// ModeAuto. This is the single place that combination logic lives - every
+// encrypt hook (SendMessageToGateway, sendMessagesReverse,
+// updateMessageContent) calls this instead of checking Enabled directly,
+// so a chat's effective behavior can never drift between call sites.
+func ShouldEncrypt(backend Backend, owner PeerID, mode Mode) (bool, error) {
+	if override, isSet, err := backend.Override(owner); err != nil {
+		return false, err
+	} else if isSet {
+		return override, nil
+	}
+
+	switch mode {
+	case ModeOn:
+		return true, nil
+	case ModeOff:
+		return false, nil
+	default:
+		return backend.Enabled(owner)
+	}
+}

e2ee/store/badgerstore/store.go

@@ -30,15 +30,19 @@ var _ libsignal.Store = (*Store)(nil)
 //
 //	<login>/<owner>/enabled
 //	<login>/<owner>/negotiatedversion
+//	<login>/<owner>/override
 //	<login>/<owner>/identity/keypair
 //	<login>/<owner>/identity/registrationid
 //	<login>/<owner>/identity/signedprekey/<id>
 //	<login>/<owner>/identity/prekey/<id>
 //	<login>/<owner>/identity/prekey/counter
 //	<login>/<owner>/remote/<remote>/identity/<deviceId>
-//	<login>/<owner>/remote/<remote>/trust/<deviceId>
+//	<login>/<owner>/remote/<remote>/blocked/<deviceId>
 //	<login>/<owner>/remote/<remote>/session/<deviceId>
 //	<login>/<owner>/remote/<remote>/devicelist
+//
+// (identity/<deviceId> doubles as the TOFU trust record - see
+// IsTrustedIdentity; there's no separate "trust" key.)
 
 func (s *Store) enabledKey() []byte {
 	return []byte(fmt.Sprintf("%s/%s/enabled", s.login, s.owner))
@@ -48,6 +52,10 @@ func (s *Store) negotiatedVersionKey() []byte {
 	return []byte(fmt.Sprintf("%s/%s/negotiatedversion", s.login, s.owner))
 }
 
+func (s *Store) overrideKey() []byte {
+	return []byte(fmt.Sprintf("%s/%s/override", s.login, s.owner))
+}
+
 func (s *Store) identityKeyPairKey() []byte {
 	return []byte(fmt.Sprintf("%s/%s/identity/keypair", s.login, s.owner))
 }
@@ -88,6 +96,10 @@ func (s *Store) remoteDeviceListKey(remote string) []byte {
 	return []byte(fmt.Sprintf("%s/%s/remote/%s/devicelist", s.login, s.owner, remote))
 }
 
+func (s *Store) blockedKey(remote string, deviceID uint32) []byte {
+	return []byte(fmt.Sprintf("%s/%s/remote/%s/blocked/%d", s.login, s.owner, remote, deviceID))
+}
+
 // --- generic byte get/set/delete/has, mirroring badger/ids.go's style ---
 
 func (s *Store) get(key []byte) ([]byte, error) {
@@ -418,6 +430,36 @@ func (s *Store) SetEnabled(enabled bool) error {
 	return s.set(s.enabledKey(), []byte{v})
 }
 
+// Override returns this chat's manual on/off override of the account-wide
+// OMEMO mode (see e2ee.Mode/e2ee.ShouldEncrypt), and whether one has been
+// set at all - isSet=false means "no override, follow the account-wide
+// mode", not "forced off".
+func (s *Store) Override() (on bool, isSet bool, err error) {
+	val, err := s.get(s.overrideKey())
+	if err != nil {
+		return false, false, err
+	}
+	if len(val) != 1 {
+		return false, false, nil
+	}
+	return val[0] == 1, true, nil
+}
+
+// SetOverride persists this chat's manual on/off override.
+func (s *Store) SetOverride(on bool) error {
+	v := byte(0)
+	if on {
+		v = 1
+	}
+	return s.set(s.overrideKey(), []byte{v})
+}
+
+// ClearOverride removes this chat's manual override, reverting it to
+// following the account-wide OMEMO mode.
+func (s *Store) ClearOverride() error {
+	return s.delete(s.overrideKey())
+}
+
 // NegotiatedVersion returns the wire-format version last negotiated for
 // this chat's outgoing content (see e2ee/omemo's Version enum - this
 // package stays version-agnostic and only stores the raw byte), and
@@ -456,3 +498,20 @@ func (s *Store) RemoteDeviceListCache(remote string) ([]byte, bool, error) {
 func (s *Store) SaveRemoteDeviceListCache(remote string, doc []byte) error {
 	return s.set(s.remoteDeviceListKey(remote), doc)
 }
+
+// IsDeviceBlocked reports whether remote's device deviceID has been
+// manually blocked - a manual override layered on top of TOFU trust
+// (IsTrustedIdentity), which always stays on regardless; this only ever
+// narrows it further. Works independent of whether a session currently
+// exists for that device.
+func (s *Store) IsDeviceBlocked(remote string, deviceID uint32) (bool, error) {
+	return s.has(s.blockedKey(remote, deviceID))
+}
+
+// SetDeviceBlocked sets or clears remote's device deviceID's manual block.
+func (s *Store) SetDeviceBlocked(remote string, deviceID uint32, blocked bool) error {
+	if !blocked {
+		return s.delete(s.blockedKey(remote, deviceID))
+	}
+	return s.set(s.blockedKey(remote, deviceID), []byte{1})
+}

e2ee/types.go

@@ -49,7 +49,11 @@ type DeviceListDoc struct{ Raw []byte }
 type BundleDoc struct{ Raw []byte }
 
 // DeviceInfo describes one known device of a peer, for trust-listing
-// ad-hoc commands.
+// ad-hoc commands. Trusted is false only if the device has been manually
+// blocked (see Backend.BlockDevice) - TOFU itself always trusts a
+// never-before-seen device automatically, so a session existing at all
+// already implies TOFU accepted it; Trusted here reflects the manual
+// override layered on top, not TOFU's own verdict.
 type DeviceInfo struct {
 	ID          DeviceID
 	Trusted     bool
@@ -162,6 +166,25 @@ type Backend interface {
 	Enabled(owner PeerID) (bool, error)
 	SetEnabled(owner PeerID, enabled bool) error
 
+	// Override, SetOverride, and ClearOverride manage owner's (an
+	// OwnedPeer) manual on/off override of the account-wide Mode (see
+	// ShouldEncrypt) - a per-chat "/omemo on"/"/omemo off" that wins
+	// regardless of the global setting, until cleared. isSet is false when
+	// no override has been set (follow the account-wide mode instead).
+	Override(owner PeerID) (on bool, isSet bool, err error)
+	SetOverride(owner PeerID, on bool) error
+	ClearOverride(owner PeerID) error
+
+	// BlockDevice and UnblockDevice manually override one of peer's
+	// devices' TOFU trust, as seen from owner's (an OwnedPeer) point of
+	// view - TOFU itself always stays on (a device's first-seen key is
+	// always trusted automatically), this only ever narrows it further. A
+	// blocked device's messages are rejected by Decrypt and skipped by
+	// Encrypt, regardless of any session already established with it - see
+	// Devices' Trusted field for the resulting per-device state.
+	BlockDevice(owner PeerID, peer PeerID, device DeviceID) error
+	UnblockDevice(owner PeerID, peer PeerID, device DeviceID) error
+
 	// Close flushes and releases whatever storage/resources this backend
 	// holds (e.g. the underlying Badger DB), for a clean process shutdown -
 	// mirrors gateway.IdsDB.Close()'s role for the id-mapping store.

persistence/sessions.go

@@ -50,6 +50,14 @@ type Session struct {
 	ignoredChatsMap map[int64]bool `yaml:"-"`
 
 	IgnoreGroupDeletions bool `yaml:":ignoregroupdeletions"`
+
+	// OMEMO is the account-wide OMEMO mode: "on", "auto", or "off" (see
+	// e2ee.Mode/e2ee.ParseMode - kept as a plain string here rather than
+	// importing the e2ee package, to avoid coupling this generic,
+	// feature-agnostic session store to one specific feature). Empty
+	// (the zero value, e.g. for an account that predates this field)
+	// means "auto", matching e2ee.ModeAuto's own default.
+	OMEMO string `yaml:":omemo"`
 }
 
 const (
@@ -70,6 +78,7 @@ var ConfigKeys = []string{
 	"receipts",
 	"nativeedits",
 	"ignoregroupdeletions",
+	"omemo",
 }
 
 var Presets = map[string][][]string{
@@ -199,6 +208,11 @@ func (s *Session) get(key string) (string, error) {
 		return fromBool(s.NativeEdits), nil
 	case "ignoregroupdeletions":
 		return fromBool(s.IgnoreGroupDeletions), nil
+	case "omemo":
+		if s.OMEMO == "" {
+			return "auto", nil
+		}
+		return s.OMEMO, nil
 	}
 
 	return "", errors.New("Unknown session property")
@@ -297,6 +311,13 @@ func (s *Session) Set(key string, value string) (string, error) {
 		}
 		s.IgnoreGroupDeletions = b
 		return value, nil
+	case "omemo":
+		switch value {
+		case "on", "auto", "off":
+			s.OMEMO = value
+			return value, nil
+		}
+		return "", errors.New("Invalid omemo mode (want on, auto, or off)")
 	}
 
 	return "", errors.New("Unknown session property")
@@ -305,7 +326,7 @@ func (s *Session) Set(key string, value string) (string, error) {
 // PropertyType determines the property type
 func PropertyType(key string) byte {
 	switch key {
-	case "timezone":
+	case "timezone", "omemo":
 		return PropertyTypeString
 	case "keeponline", "rawmessages", "asciiarrows", "muc", "oobmode", "carbons", "hideids",
 		"receipts", "nativeedits", "ignoregroupdeletions":

telegram/commands.go

@@ -70,6 +70,7 @@ var transportCommands = map[string]command{
 	"supergroup":  command{1, []string{"title", "description"}, "create new supergroup «title» with «description»", true, nil, true},
 	"channel":     command{1, []string{"title", "description"}, "create new channel «title» with «description»", true, nil, true},
 	"preset":      command{1, []string{"modern|classic|pass"}, "apply a config preset", false, nil, false},
+	"omemo":       command{0, []string{"on|auto|off"}, "view or set the account-wide OMEMO encryption mode", false, nil, false},
 	"pass":        command{0, []string{}, "proceed to next login stage", false, nil, false},
 	"finish":      command{0, []string{}, "skip post-login configuration", false, nil, false},
 }
@@ -88,6 +89,7 @@ var chatCommands = map[string]command{
 	"raw":        command{1, []string{"message"}, "send a raw message not interpeted as a transport command (e.g. a bot command)", true, nil, true},
 	"forward":    command{2, []string{"message_id", "target_chat"}, "forwards a message", true, nil, true},
 	"vcard":      command{0, []string{}, "print vCard as text", true, nil, true},
+	"omemo":      command{0, []string{"[on|off|clear|devices ...]"}, "view or override this chat's OMEMO state, or manage its peer's device trust (devices list|block <id>|accept <id>)", true, nil, false},
 	"add":        command{1, []string{"@username"}, "add @username to your chat list", true, nil, true},
 	"join":       command{1, []string{"https://t.me/invite_link"}, "join to chat via invite link or @publicname", true, nil, true},
 	"group":      command{1, []string{"title"}, "create groupchat «title» with current user", true, &notForGroups, true},
@@ -126,6 +128,7 @@ var transportConfigurationOptions = map[string]configurationOption{
 	"receipts":             configurationOption{"<bool>", "if enabled, XMPP read receipts are synced to Telegram, otherwise, messages are marked as read automatically (true/false)"},
 	"nativeedits":          configurationOption{"<bool>", "if possible, edit XMPP messages instead of showing Telegram edits as separate messages (true/false)"},
 	"ignoregroupdeletions": configurationOption{"<bool>", "suppress message deletion messages in group chats (true/false)"},
+	"omemo":                configurationOption{"<on|auto|off>", "account-wide OMEMO encryption mode - see /omemo for a dedicated command and per-chat overrides"},
 }
 
 type command struct {
@@ -572,6 +575,17 @@ func (c *Client) ProcessTransportCommand(cmdline string, resource string) (strin
 			cancelNextStage = true
 			return "Invalid argument. Allowed ones are " + transportCommands["preset"].Arguments[0], false
 		}
+	case "omemo":
+		if len(args) > 0 {
+			value, err := c.Session.Set("omemo", args[0])
+			if err != nil {
+				return err.Error(), false
+			}
+			gateway.DirtySessions = true
+			return fmt.Sprintf("omemo mode set to %s", value), true
+		}
+		value, _ := c.Session.Get("omemo")
+		return fmt.Sprintf("omemo mode is set to %s (per-chat overrides: use /omemo on|off|clear in a chat)", value), true
 	case "pass":
 		switch c.loginStage {
 		case LoginStagePreset:
@@ -1180,6 +1194,9 @@ func (c *Client) ProcessChatCommand(chatID int64, cmdline string) (string, bool,
 		}
 
 		return strings.Join(entries, "\n"), true, true
+	case "omemo":
+		response, success := c.cmdOmemoChat(chatID, args)
+		return response, true, success
 	case "help":
 		return c.helpString(CommandTypeChat, chatID), true, true
 	default:

telegram/handlers.go

@@ -418,7 +418,13 @@ func (c *Client) updateMessageContent(update *client.UpdateMessageContent) {
 			if !isMUC {
 				if backend, ok := gateway.E2EE.Backend(); ok {
 					owner := e2ee.OwnedPeer(c.Session.Login, gateway.CHATJID(update.ChatId, false))
-					if active, _ := backend.Enabled(owner); active {
+					mode, modeErr := e2ee.ParseMode(c.Session.OMEMO)
+					if modeErr != nil {
+						log.Error(errors.Wrap(modeErr, "Invalid omemo mode"))
+					}
+					if active, err := e2ee.ShouldEncrypt(backend, owner, mode); err != nil {
+						log.Error(errors.Wrap(err, "Failed to evaluate OMEMO policy"))
+					} else if active {
 						peer := e2ee.PeerID(c.jid)
 						if err := c.ensureOMEMOSession(backend, owner, peer); err != nil {
 							log.Error(errors.Wrap(err, "Failed to establish OMEMO session"))

telegram/omemo_commands.go

@@ -0,0 +1,129 @@
+package telegram
+
+import (
+	"fmt"
+	"strings"
+
+	"dev.narayana.im/narayana/telegabber/e2ee"
+	"dev.narayana.im/narayana/telegabber/xmpp/gateway"
+)
+
+// cmdOmemoChat implements the chat-scoped "/omemo" command: with no
+// arguments, reports this chat's current OMEMO state (account-wide mode,
+// any override, and the resulting effective state); "on"/"off" forces this
+// specific chat regardless of the account-wide mode (persistence.Session.OMEMO,
+// via e2ee.Mode/e2ee.ShouldEncrypt); "clear" removes that override, reverting
+// to following the account-wide mode; "devices ..." manages this chat's
+// peer's device trust (see cmdOmemoDevices).
+func (c *Client) cmdOmemoChat(chatID int64, args []string) (string, bool) {
+	backend, ok := gateway.E2EE.Backend()
+	if !ok {
+		return "OMEMO is not enabled on this transport", false
+	}
+	owner := e2ee.OwnedPeer(c.Session.Login, gateway.CHATJID(chatID, false))
+
+	if len(args) == 0 {
+		return c.omemoChatStatus(backend, owner)
+	}
+
+	switch args[0] {
+	case "on", "off":
+		if err := backend.SetOverride(owner, args[0] == "on"); err != nil {
+			return err.Error(), false
+		}
+		return fmt.Sprintf("OMEMO forced %s for this chat", args[0]), true
+	case "clear":
+		if err := backend.ClearOverride(owner); err != nil {
+			return err.Error(), false
+		}
+		return "OMEMO override cleared for this chat, now following the account-wide mode", true
+	case "devices":
+		return c.cmdOmemoDevices(backend, owner, args[1:])
+	default:
+		return "Usage: /omemo [on|off|clear|devices list|devices block <id>|devices accept <id>]", false
+	}
+}
+
+func (c *Client) omemoChatStatus(backend e2ee.Backend, owner e2ee.PeerID) (string, bool) {
+	mode, err := e2ee.ParseMode(c.Session.OMEMO)
+	if err != nil {
+		return err.Error(), false
+	}
+	override, isSet, err := backend.Override(owner)
+	if err != nil {
+		return err.Error(), false
+	}
+	active, err := e2ee.ShouldEncrypt(backend, owner, mode)
+	if err != nil {
+		return err.Error(), false
+	}
+
+	overrideText := "not set (following the account-wide mode)"
+	if isSet {
+		overrideText = fmt.Sprintf("forced %s", onOffString(override))
+	}
+
+	return fmt.Sprintf("Account-wide mode: %s\nThis chat's override: %s\nEffective right now: %s",
+		mode, overrideText, onOffString(active)), true
+}
+
+// cmdOmemoDevices lists, blocks, or accepts (unblocks) devices of owner's
+// chat's real peer. TOFU trust itself always stays on (a never-before-seen
+// device is always trusted automatically) - block/accept only manage a
+// manual override layered on top of that, per Backend.BlockDevice's doc
+// comment.
+func (c *Client) cmdOmemoDevices(backend e2ee.Backend, owner e2ee.PeerID, args []string) (string, bool) {
+	peer := e2ee.PeerID(c.jid)
+
+	sub := "list"
+	if len(args) > 0 {
+		sub = args[0]
+	}
+
+	switch sub {
+	case "list":
+		devices, err := backend.Devices(owner, peer)
+		if err != nil {
+			return err.Error(), false
+		}
+		if len(devices) == 0 {
+			return "No known devices for this chat's peer yet", true
+		}
+		lines := make([]string, 0, len(devices))
+		for _, d := range devices {
+			lines = append(lines, fmt.Sprintf("%s: %s", d.ID, trustString(d.Trusted)))
+		}
+		return strings.Join(lines, "\n"), true
+	case "block", "accept":
+		if len(args) < 2 {
+			return notEnoughArguments, false
+		}
+		device := e2ee.DeviceID(args[1])
+		var err error
+		if sub == "block" {
+			err = backend.BlockDevice(owner, peer, device)
+		} else {
+			err = backend.UnblockDevice(owner, peer, device)
+		}
+		if err != nil {
+			return err.Error(), false
+		}
+		return fmt.Sprintf("Device %s %sed", device, sub), true
+	default:
+		return "Usage: /omemo devices [list|block <id>|accept <id>]", false
+	}
+}
+
+func onOffString(b bool) string {
+	if b {
+		return "on"
+	}
+	return "off"
+}
+
+func trustString(trusted bool) string {
+	if trusted {
+		return "trusted"
+	}
+	return "blocked"
+}

telegram/utils.go

@@ -2062,10 +2062,12 @@ func (c *Client) SendMessageToGateway(chatId int64, message *client.Message, id
 
 	// OMEMO encrypt hook - personal-chat pseudo-JIDs only (true MUC/XEP-0045
 	// groupchat OMEMO is out of scope entirely, not deferred - see the plan
-	// doc), gated on the per-chat active flag set by the decrypt hook's
-	// auto-upgrade trigger (xmpp/handlers.go). The account-wide config
-	// toggle (persistence.Session.OMEMO) is a separate, not-yet-wired-up
-	// piece (M4) meant to OR into this same gate. Encryption happens once
+	// doc). Whether to encrypt is decided by e2ee.ShouldEncrypt, combining
+	// this chat's optional /omemo on|off override, the account-wide
+	// persistence.Session.OMEMO mode, and (for the default "auto" mode) the
+	// per-chat active flag set by the decrypt hook's auto-upgrade trigger
+	// (xmpp/handlers.go) - see ShouldEncrypt's own doc comment for the
+	// combination rules. Encryption happens once
 	// per logical message (not once per jids resource copy), addressed to
 	// every known device of the real user's bare JID - carbon-copy
 	// resources all share the same OMEMO device fan-out. OOB file links are
@@ -2083,7 +2085,13 @@ func (c *Client) SendMessageToGateway(chatId int64, message *client.Message, id
 	if !isGroupchat && needsOMEMOEncryption {
 		if backend, ok := gateway.E2EE.Backend(); ok {
 			owner := e2ee.OwnedPeer(c.Session.Login, gateway.CHATJID(chatId, false))
-			if active, _ := backend.Enabled(owner); active {
+			mode, modeErr := e2ee.ParseMode(c.Session.OMEMO)
+			if modeErr != nil {
+				log.Error(errors.Wrap(modeErr, "Invalid omemo mode"))
+			}
+			if active, err := e2ee.ShouldEncrypt(backend, owner, mode); err != nil {
+				log.Error(errors.Wrap(err, "Failed to evaluate OMEMO policy"))
+			} else if active {
 				peer := e2ee.PeerID(c.jid)
 				if err := c.ensureOMEMOSession(backend, owner, peer); err != nil {
 					log.Error(errors.Wrap(err, "Failed to establish OMEMO session"))
@@ -3047,7 +3055,13 @@ func (c *Client) sendMessagesReverse(chatID int64, messages []*client.Message, p
 			if !isMUC && body != "" {
 				if backend, ok := gateway.E2EE.Backend(); ok {
 					owner := e2ee.OwnedPeer(c.Session.Login, gateway.CHATJID(chatID, false))
-					if active, _ := backend.Enabled(owner); active {
+					mode, modeErr := e2ee.ParseMode(c.Session.OMEMO)
+					if modeErr != nil {
+						log.Error(errors.Wrap(modeErr, "Invalid omemo mode"))
+					}
+					if active, err := e2ee.ShouldEncrypt(backend, owner, mode); err != nil {
+						log.Error(errors.Wrap(err, "Failed to evaluate OMEMO policy"))
+					} else if active {
 						peer := e2ee.PeerID(c.jid)
 						if err := c.ensureOMEMOSession(backend, owner, peer); err != nil {
 							log.Error(errors.Wrap(err, "Failed to establish OMEMO session"))